Brake mechanism

Abstract

A park brake mechanism includes a sealed housing enclosing a brake disc pack which is normally pressed together by a plurality of coil compression springs acting between an end of the housing and a pressure plate. Four hydraulic pistons are reciprocably mounted in the opposite end of the housing and connecting pins are received between the pistons and the pressure plate and serve to effect the release of the braking action between the disc pack discs when the pistons are pressurized. The pistons are in a rectangular pattern and diagonally opposite ones have threaded ports aligned therewith and adapted for receiving screws for stroking the pistons in the absence of pressure. A fluid pressure passage leading to the pistons contains a one-way orifice which operates to modulate the application of the brakes when pressure is relieved from the pistons.

I claim: 
     
       1. A park brake mechanism arranged for selectively applying a braking force to a drive shaft, comprising: a fixed housing assembly disposed annularly about an end of said drive shaft; one end of said housing assembly having four cylindrical bores arranged in a generally rectangular configuration and opening axially toward an opposite end of the housing assembly; a fluid passage interconnecting the bores; a piston received in each bore; a threaded port leading axially into a diagonally disposed pair of the bores; screw means for selected threaded reception in each of said ports for stroking an associated piston; a disc pack located in the housing assembly and including first disc members fixed to the housing assembly and second disc members interleaved with the first disc members and fixed for rotation with the shaft; a pressure plate axially, shiftably mounted in the housing assembly adjacent a first end of the disc pack which is remote from the pistons; connecting pins respectively mounted with opposite ends engaging said pistons and the pressure plate; a plurality of coil compression springs mounted between said opposite end of said housing assembly and said pressure plate for effecting engagement of the brake in the absence of fluid pressure acting on the pistons; said housing assembly including a disc pack housing sandwiched between and separable from a spring housing and a piston housing, with the spring and piston housings defining said one and opposite ends of said housing assembly; releasable securing means including a first set of fasteners for securing only the disc pack and piston housings together in a subassembly and a second set of fasteners for fixing the spring and piston housings to the disc pack housing in full assembly; and said first set of fasteners including said screw means whereby said screw means is always readily available for stroking said pistons.